Nitric acid

Nitric acid is a liquid chemical utilized in the manufacturing processes for compounds found in fertilizers, dyes, explosives, and other substances. Nitric acid is an important industrial chemical in the United States. However, it releases dangerous fumes and presents a fire and explosion risk. Despite this, nitric acid has many scientific and commercial uses.

Background

The origins of nitric acid are somewhat ambiguous. There is some dispute about the identity of the person thought to have discovered nitric acid and confusion regarding the name of the substance itself. Nitric acid appears to have been known by the year 1300, when it was called aqua fortis, or “strong water.” An Arabic alchemist named Jābir ibn Ḥayyān, whose name is Latinized in Europe as Geber, is thought to have first discovered nitric acid. Still, there is some evidence that nitric acid was known before Geber wrote about it, and some scholars doubt Geber ever actually existed.

Nevertheless, the writing attributed to Geber included a formula for making nitric acid. The formula is generally credited with introducing nitric acid to the scientific world. This was an important advancement because nitric acid gave alchemists new ways to approach a number of experiments they had been struggling with, such as separating gold from other metals. By the 1600s, nitric acid was used for many tasks in which strong solvents were needed.

German-Dutch apothecary Johann Rudolf Glauber developed a new way to make nitric acid in 1648. He accomplished this by mixing concentrated sulfuric acid and potassium nitrate and then heating the mixture. Over the next several centuries, a number of other individuals made discoveries regarding the creation of nitric acid. In 1901, German chemist Wilhelm Ostwald developed a process for making nitric acid by oxidizing ammonia and converting the resulting nitrogen oxides into nitric acid. This process, which became known as the Ostwald process, made it possible to create large amounts of nitric acid for the production of fertilizers. The process is also used to produce dyes, pharmaceuticals, rocket fuel, and explosives.

Overview

Nitric acid is also known as hydrogen nitrate and engraver’s acid. While it is naturally clear, nitric acid tends to turn yellow when stored for long periods. This is caused by an accumulation of nitrogen oxides during storage. Normally, nitric acid has a concentration of 68 percent. When it reaches a level of 86 percent or higher, it is known as fuming nitric acid. Fuming nitric acid can be further divided into white or red fuming nitric acid, depending on the amount of nitrogen dioxide the solution contains.

The fumes from nitric acid have a characteristic choking odor. The smell is alternately described as cloyingly sweet or very acrid and harsh. Breathing in nitric acid fumes can result in a feeling of being suffocated.

In industrial production, nitrogen oxides formed from ammonia are absorbed in water to produce nitric acid. Its level of purity can be manipulated through the addition of substances such as sulfuric acid. Scientists can also alter nitric acid through the application of heat or the use of a condenser that removes fumes. Still, the Ostwald process is the most common method of producing nitric acid in the twenty-first century. Nitric acid production can generate nitrous oxide, a greenhouse gas, and some production facilities use emission-control systems to reduce these emissions.

Nitric acid has a number of applications. It is a powerful solvent that is commonly used in laboratories to acidify samples during some chloride-ion tests, and it is used in tests that distinguish between heroin and morphine and identify alkaloids, such as the drug lysergic acid diethylamide (LSD).

There are also many commercial applications for nitric acid. It is used for some medical purposes, including the removal of warts. Nitric acid is also used to finish or engrave metal and to change the color of wood in some wood-production applications. It also plays a role in the production of rubber and in the treatment process for spent nuclear fuel. Its most significant use is in the production of ammonium nitrate, which is widely used in fertilizers and industrial explosives. Nitric acid is also used in the manufacture of explosives, such as trinitrotoluene (TNT) and nitroglycerin.

Although nitric acid is not flammable, it is a strong oxidizer that can intensify fires and react violently with incompatible materials. Nitric acid is also a strong corrosive that can dissolve metal. This means it requires special handling, and it must be kept in tanks designed to resist its corrosive effects. It is important to separate nitric acid from a number of organic chemicals, including acetic acid, acetic anhydride, and acetone. Reactions between nitric acid and any of these chemicals can trigger fires and cause explosions.

Nitric acid presents other hazards as well. It is highly destructive to all parts of the human body, whether contact is from the liquid or the fumes. It has even been known to erode tooth enamel, particularly the enamel of the front teeth in people who routinely handle the chemical. Both the fumes and the liquid form can cause severe damage to the eyes, which may result in blindness. Skin contact with nitric acid can cause severe chemical burns and scarring. Inhaling the fumes can lead to effects ranging from a cough and irritation to spasms of the larynx, pulmonary edema (when the lungs fill with fluid), and breathing difficulties. Symptoms of lung injury may not appear immediately after exposure. If the acid is ingested or swallowed, it can result in burns to the digestive system and perforation or necrosis (tissue death) of the stomach.

Bibliography

Di Justo, Patrick. “The Fertilizer Bomb.” The New Yorker, 18 Apr. 2013, www.newyorker.com/tech/elements/the-fertilizer-bomb. Accessed 5 June 2026.

“How Is Nitric Oxide Used?” Washington University, faculty.washington.edu/finlayso/che499/Group_C/how%20is%20nitric%20oxide%20used.htm. Accessed 5 June 2026.

Karpenko, Vladimir. “Some Notes on the Early History of Nitric Acid: 1300–1700.” Bulletin for the History of Chemistry, vol. 34, no. 2, 2009, pp. 105–16, www.researchgate.net/publication/50890162_Some_notes_on_the_early_history_of_nitric_acid_1300-1700. Accessed 5 June 2026.

“NIOSH Pocket Guide to Chemical Hazards: Nitric Acid.” The National Institute for Occupational Safety and Health, www.cdc.gov/niosh/npg/npgd0447.html. Accessed 5 June 2026.

“Nitric Acid.” The Chemical Company, thechemco.com/chemical/nitric-acid/. Accessed 5 June 2026.

“Nitric Acid.” Department of Climate Change, Energy, the Environment and Water, 2 June 2026, www.dcceew.gov.au/environment/protection/npi/substances/fact-sheets/nitric-acid. Accessed 5 June 2026.

“Nitric Acid Safety Data Sheet.” 4 June 2024, www.cfindustries.com/globalassets/cf-industries/media/documents/safety-data-sheets/nitric-acid---na/nitric-acid----updated-address-4-june-2024.pdf. Accessed 5 June 2026.

“Nitric Acid Storage: Tank Selection, Safety Limits, and Best Practices.” PolyProcessing, blog.polyprocessing.com/blog/nitric-acid-storage-and-common-uses. Accessed 5 June 2026.

“Poison Facts: High Chemicals: Nitric Acid.” The University of Kansas Hospital, www.kansashealthsystem.com/~/media/Imported/kumed/documents/nitricoxide.ashx?la=en. Accessed 5 June 2026.

“Subpart V—Nitric Acid Production.” United States Environmental Protection Agency, www.epa.gov/ghgreporting/subpart-v-nitric-acid-production. Accessed 5 June 2026.